When human strength meets plant fragility: how recreational rock climbing intensity affects cliff bryophytes

Aim Cliff ecosystems are globally widespread but remain insufficiently studied, particularly with respect to cryptogamic, spore-producing plants. We assessed how recreational rock climbing and associated climbing-use intensity influence bryophyte communities, and how these effects interact with the vertical environmental gradient. Location Limestone cliffs of the Kraków–Częstochowa Upland, southern Poland. Methods We compared three climbing-use categories: (i) uncleaned cliffs not used for climbing (controls), (ii) cleaned cliffs with climbing routes that are used frequently (high-use; higher disturbance), and (iii) cleaned cliffs with infrequently used routes (low-use, lower disturbance). Bryophytes were sampled along four vertical transects per climbing-use category (12 in total), using 1 × 1 m plots placed every 2 m from the base to approximately 12 m height. We analysed bryophyte cover, proportional contribution to total vegetation cover, species richness, life-strategy composition and community structure using generalized linear mixed models and multivariate analyses. Results Bryophyte cover was significantly reduced on both types of cleaned cliffs compared with controls and exhibited a U-shaped pattern along the vertical gradient, with a minimum at mid- wall positions. Bryophyte vegetation cover was also lower on cleaned cliffs, whereas vascular plant cover did not differ among climbing-use categories. The proportional contribution of bryophytes declined most strongly at mid-wall positions on highly used cliffs. Bryophyte species richness was highest on uncleaned cliffs, while taxonomic diversity and life-strategy composition showed no significant differences. Community composition showed significant but weak vertical structuring, while differences among climbing-use categories were detectable at the cliff-face level. Conclusions Recreational climbing and route cleaning are associated with substantial reductions in bryophyte cover and species richness on limestone cliffs, with limited effects on flowering plant cover. Conservation of bryophyte diversity in cliff ecosystems may require the retention of uncleaned cliff faces and restrictions on route cleaning, particularly in mid-wall zones most sensitive to disturbance.